This invention relates to turbogenerators, and more specifically to electrical braking systems and associated control algorithms for integrated turbogenerators. Conventional integrated turbogenerator systems can become unstable during transient operating conditions. Known techniques for enhancing stability often lead to inefficient operation. What is now needed is a technique for ensuring stable operation of integrated turbogenerators while minimizing associated inefficiencies.
In one aspect, the present invention provides an integrated turbogenerator system comprising a turbine, a compressor rotationally coupled to the turbine for rotating therewith to generate compressed air, a combustor fluidly coupled to the compressor for combusting fuel and the compressed air therein to generate exhaust gas to drive the turbine, a generator rotationally coupled to the turbine for rotating therewith to generate electric power, and an electrically resistive device connected to the generator to selectively dissipate a portion of the generated power.
In another aspect of the present invention, the compressor further comprises an air intake disposed in a preselected relationship to the resistive device to channel air over the resistive device and into the compressor. The electrically resistive device may connected to the generator to selectively dissipate a portion of the generated power as thermal energy in the air channeled into the compressor.
In a further aspect of the present invention, the turbogenerator system also comprises a controller connected to the generator and to the resistive device to selectively supply a portion of the generated power from the generator to the resistive device. The controller may supply a portion of the generated power from the generator to the resistive device in accordance with variations in a load on the generator. The controller may also control the speed of the turbine in accordance with variations in the load, and/or in accordance with a temperature of the resistive device, such as to maintain a temperature of the resistive device below a preselected value.
In yet another aspect of the invention, the controller reduces the speed of the turbine in response to a reduction in the load and supplies at least a portion of any generated power in excess of the load to the resistive device, the controller reducing the turbine speed at a rate selected to maintain a temperature of the resistive device below a preselected value.
These and other features and advantages of this invention will become further apparent from the detailed description and accompanying figures that follow. In the figures and description, numerals indicate the various features of the invention, like numerals referring to like features throughout both the drawing figures and the written description.